Grazing of Evechinus chloroticus (Kina) on Species Caulerpa brachypus and Caulerpa parvifolia, Two Invasive Species of Seaweed in New Zealand

Abstract

As the two invasive species (Caulerpa brachypus and C. parvifolia) proliferate within New Zealand waters, there is a growing imperative to identify potential strategies for controlling its spread. This study investigates the prospect of leveraging the New Zealand sea urchin Evechinus chloroticus (kina) as a bio-control mechanism against the current Caulerpa outbreak. The research endeavours to test Kina's feeding preferences towards Caulerpa seaweed through a laboratory based investigation spanning four weeks. Three dietary treatments were employed to gauge the kina's response to Caulerpa consumption vs. native Ecklonia radiata seaweed.

Our results show that that kina did consume Caulerpa spp. when presented with only Caulerpa spp. and when presented with both E. radiata and Caulerpa spp.. Unfortunately, our findings must be interpreted with caution, given that this was lab based and that the kina tended to consume 100% of the seaweed presented to them (both E. radiata and Caulerpa spp.); this truncation of the data precluding detailed statistical analysis. Consuming Caulerpa spp. did not have any detectable deleterious impacts on the kina, in fact all animals across all treatments increased condition (using gonad growth as a condition index) with no statistically significant difference between the three treatments.